NEW YORK -- They look like wanted posters, but they don't show Mohamed Atta or Osama bin Laden.

Instead, the glossy FBI posters plastered around Ground Zero and at the Fresh Kills landfill, where the wreckage of the World Trade Center is being sifted, show components of airplane "black boxes," some twisted and burned from previous crashes. Law enforcement officials are hoping against hope that agents -- or even people in nearby buildings -- may yet stumble upon the valuable equipment and that the information inside...